FR3068990B1 - ELECTROCHEMICAL DEVICE COMPRISING A HYDROGEN SENSOR - Google Patents

Abstract

The invention relates to an electrochemical device comprising at least one electrochemical cell (10), comprising: - a membrane electrode assembly and bipolar plates traversed by at least one evacuation collector (15.1), the membrane electrode assembly comprising a zone active (2) and a connecting zone (3); at least one hydrogen sensor (30) comprising an anode (31) positioned in the connection zone (3) and including a catalyst adapted to ensure the oxidation of hydrogen, and a cathode (32) facing the anode (31); a source of tension; a current sensor; a calculation unit (36) adapted to detect the presence of hydrogen from the measured value of the electric current.

Description

ELECTROCHEMICAL DEVICE COMPRISING A HYDROGEN SENSOR

TECHNICAL AREA

The field of the invention is that of the detection of the presence of hydrogen in an electrochemical device comprising a proton exchange membrane, such as a fuel cell or an electrolyzer.

STATE OF THE PRIOR ART

[002] Electrochemical electrolyte exchange membrane proton devices, such as a fuel cell or an electrolyzer, usually comprise one or more electrochemical cells each having a membrane electrode assembly (AME), the latter being formed of an anode and a cathode separated from each other by the electrolyte membrane.

[003] In the case of an electrolyser, when water is supplied to the anode and a potential difference is applied to the electrodes, the oxidation of the water is carried out, thus producing oxygen and protons. The latter migrate through the electrolyte membrane to the cathode where a reduction of the protons is produced, thus producing hydrogen. In the case of a fuel cell, the anode oxidizes the introduced hydrogen, and the cathode produces water by a reduction reaction from the oxygen introduced, and protons and electrons from of the anode.

[004] However, the electrolyte membrane has a non-zero coefficient of permeation with respect to hydrogen, so that hydrogen can diffuse permeate through the membrane to the opposite electrode. Thus, in the case of the electrolyser, hydrogen can diffuse to the anode and mix with the oxygen produced, which can lead to a risk of ignition when the volume fraction of hydrogen the absence of liquid water becomes greater than about 4%. In the case of a fuel cell, a high proportion of hydrogen at the cathode may reflect the presence of a structural degradation of the electrolyte membrane, for example membrane aging or local failure.

[005] There is therefore a need to detect the presence of hydrogen diffused by permeation through the electrolyte membrane proton exchange in electrochemical devices equipped with such membranes.

STATEMENT OF THE INVENTION

The invention aims to remedy at least in part the disadvantages of the prior art, and more particularly to provide an electrochemical device with electrolyte membrane proton exchange comprising a hydrogen sensor.

[007] For this, the object of the invention is an electrochemical device an electrode membrane assembly formed of an electrolyte membrane proton exchange, a first electrode in contact with a first face of the membrane, and a second electrode in contact with a second opposite face of the membrane; and two bipolar plates, between which is located the membrane electrode assembly, traversed by at least a first evacuation collector in fluid communication with the first face of the membrane; the electrode membrane assembly comprising an active zone delimited by the first and second electrodes, and a connection zone situated between the active zone and the first evacuation collector.

[008] According to the invention, the electrochemical device comprises at least one hydrogen sensor, comprising: an anode positioned in the bonding zone in contact with the first face and including a catalyst adapted to ensure the oxidation of hydrogen , and a cathode in contact with the second face and located opposite the anode; a voltage source adapted to apply an electrical voltage between the anode and the cathode by an electric circuit; a current sensor, connected to the voltage source, adapted to measure the electric current flowing in the electrical circuit; a calculation unit, connected to the current sensor, adapted to detect the presence of hydrogen at the first face from the measured value of the electric current.

[009] Some preferred but non-limiting aspects of this electrochemical device are as follows.

The calculation unit can be adapted to calculate the amount of oxidized hydrogen at the anode from the measured value of the electric current.

The calculation unit can be adapted to calculate the amount of hydrogen flowing in the connection zone at the first face, from the measured value of the electric current.

A first bipolar plate may include a first fluid distribution circuit in communication with said first flow collector and having at least one distribution channel superimposed on the anode.

Each bipolar plate may be formed of at least one sheet made of an electrically conductive material.

The anode and the cathode can be electrically isolated from the bipolar plates.

The electrolytic membrane may comprise a projecting portion located in a border of the connection zone, the voltage source comprising a first conductive track secured to the first face of the membrane and connecting the anode to the projecting portion, and a second conductive track secured to the second face and connecting the cathode to the projecting portion.

The first and second conductive tracks may have a thickness less than or equal to 1opm.

A first and a second bipolar plate may each be formed of a plate made of an electrically insulating material, and comprising conductive lines arranged so as to polarize, respectively, the first electrode independently of the anode, and the second electrode. independently of the cathode.

The first bipolar plate can be made in one piece, and has an inner face and an outer face, the inner face having structures forming a fluid distribution circuit, the first bipolar plate being adapted to apply a first potential. electrical to the first electrode and a second electrical potential to the anode different from the first potential.

The insulating material of the first bipolar plate may define the inner face and the opposite outer face, the inner face having fluidic distribution channels longitudinally separated in pairs by a longitudinal wall coming into contact with the first electrode or the second electrode. anode by a bearing surface, electrically conductive lines extending at the longitudinal wall bearing surfaces and being adapted, for a first set of them, to apply to the first electrode an electric potential and, for a second set of them, to apply to the anode a different electrical potential.

The first bipolar plate may comprise a first and a second conductive lines called contact recovery extending on the outer face, and first and second conductive vias extending between the outer face and the inner face in the walls. longitudinal, the first conductive line of contact recovery being adapted to apply an electrical potential to the first set of conductive lines by conductive vias, and the second conductive line of contact recovery being adapted to apply a different electrical potential to the second set of lines conductive by the other conductive vias.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, objects, advantages and features of the invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and with reference to the accompanying drawings in which: Figure 1 is an exploded perspective view of an example of an electrochemical device according to the prior art, comprising a stack of electrochemical cells each having a membrane electrode assembly (AME); Figure 2 is a schematic longitudinal sectional view of an electrochemical device according to one embodiment, comprising a hydrogen sensor having electrodes located in a connection zone of the electrode membrane assembly;

FIGS. 3A to 3E are schematic views from above of different parts of an electrochemical device according to a first variant of the embodiment, in which the bipolar plates are of conductive sheet type: FIG. 3A illustrates a bipolar plate covering a AME; FIGS. 3B and 3C illustrate an AME, on the side of the first electrode (FIG. 3B) and on the side of the second electrode (FIG. 3C), the membrane of which has a projection up to which a track extends. conductor in contact with the anode or the cathode of detection; FIGS-3D and 3E illustrate a diffusion layer having a through-orifice (FIG. 3D), the latter covering the first electrode of the active zone, so that the through-orifice is positioned opposite the anode of FIG. detection (fig.3E);

FIG. 4 is a schematic view from above of the AME according to another variant of the embodiment, comprising a plurality of hydrogen sensors positioned at the outlet of one or more fluid distribution channels;

FIGS. 5A and 5B are schematic views of an electrochemical device according to a second variant of the embodiment, in which the bipolar plates are of printed circuit board type (PCB): FIG. 5A illustrates FIG. in a top view, on the side of the first electrode, an AME covered by distribution channels; FIG. 5B illustrates a portion of the electrochemical device in cross-section along the plane A-A illustrated in FIGS.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

In the figures and in the following description, the same references represent identical or similar elements. In addition, the various elements are not represented on the scale so as to favor the clarity of the figures. Moreover, the various embodiments and variants are not exclusive of each other and can be combined with each other. Unless otherwise indicated, the terms "substantially", "about", "of the order of" mean within 10%.

FIG. 1 illustrates an example of an electrochemical device 1 according to the prior art, here as described in document WO2OO4 / 102710, comprising a stack of electrochemical cells 10 with an electrolyte exchange membrane of protons.

We define here and for the rest of the description a three-dimensional orthogonal direct reference (Χ, Υ, Ζ), where the X and Y axes are oriented along the plane of the electrolytic membrane of each electrochemical cell 10, the axis X being oriented along the main direction of anodic fluid flow, and where the Z axis is oriented orthogonal to the XY plane.

Each electrochemical cell 10 comprises an electrode membrane assembly 11 (AME) formed of a first electrode, for example an anode in the case of an electrolyzer, and a second electrode, for example a cathode, separated from the electrode. one from the other by an electrolyte membrane proton exchange. The anode, the membrane and the cathode are conventional elements known to those skilled in the art. Each MEA 11 extends along a main plane of the electrolytic membrane parallel to the XY plane. Gas diffusion layers 12 (GDL, for Gas Diffusion Rent, in English) here cover the electrodes.

Each AME 11 is separated from that of the adjacent cells by bipolar plates 13. Each bipolar plate 13 has a face intended to be partially in contact with the first electrode of a cell 10, and another opposite face intended to be partially in contact with the second electrode of the adjacent cell. Each bipolar plate 13 is adapted to bring the reactive species to the anode of a first cell 10 on the one hand and to the cathode of an adjacent cell 10 on the other hand, by means of fluid distribution circuits, and to evacuate the products resulting from the electrochemical reactions and the non-reactive species by these same distribution circuits, as well as to transmit the electric current between the cells 10. It can also ensure, particularly in the case of fuel cells, the flow of a heat transfer fluid between the cells 10 so as to allow the evacuation of the heat produced.

The electrochemical device 1 also comprises separate flow collectors 14, 15, each formed of an opening which passes through the stack of cells 10, and more precisely which passes through the bipolar plates 13 opposite a border of ΓΑΜΕ n. Injection manifolds 14 ensure the injection of reactive fluids from injection ports 16, and evacuation manifolds 15 allow the evacuation of electrochemical reaction products to discharge ports 17.

Thus, in general, each electrochemical cell 10 comprises a first distribution circuit connecting a first injection manifold to a first exhaust manifold, adapted to bring the incoming reactive fluid Fi, m into contact with the first electrode. A second distribution circuit connects a second injection manifold to a second exhaust manifold adapted to ensure that another incoming reactive fluid F2 is brought into contact with the second electrode.

FIG. 2 schematically illustrates, in longitudinal section, an electrochemical device 1 according to one embodiment comprising an electrochemical cell 10 equipped with a hydrogen sensor 30.

The electrochemical cell 10 comprises two bipolar plates 13.1, 13.2 between which is located an AME 11. Each bipolar plate 13.1, 13.2 comprises a distribution circuit 18.1, 18.2 of a fluid adapted to ensure the flow of a fluid at an electrode 21,22 of ΓΑΜΕ n between two flow collectors, more precisely between an injection manifold 14.1, 14.2 and an evacuation manifold 15.1, 15.2. The distribution circuit 18.1, 18.2 is formed of an array of distribution channels which extend between an inlet communicating with the injection manifold 14.1, 14.2 and an outlet communicating with the exhaust manifold 15.1, 15.2. The first bipolar plate 13.1 makes it possible to bring a reactive fluid to a first electrode 21 of ΓΑΜΕ n, and the second bipolar plate 13.2 allows the flow of another fluid to and / or from the second electrode 22.

The electrode membrane assembly 11 comprises a same electrolyte membrane 19 proton exchange separating firstly the first electrode 21 of the second electrode 22 located opposite one another, and secondly an anode 31 of a cathode 32 of the detection sensor 30 located opposite one another.

The first and second electrodes 21, 22 define the active zone 2 of ΓΑΜΕ n. Also, ΓΑΜΕ n comprises the active zone 2 and a so-called connection zone 3, the latter being located between the active zone 2 and a flow collector 15.1, and more precisely between the active zone 2 and the first collector evacuation 15.1. Thus, the electrolyte membrane 19 is coated with the first and second electrodes 21, 22 in the active zone 2 only and not in the connection zone 3. In the active zone 2, electrochemical reactions taking place participate in the electrochemical efficiency of the device 1: the active zone 2 is thus the place of the electrolysis of water in the case of an electrolyser, and the place of the water generation by reaction of hydrogen and oxygen in the case of a Fuel cell. Also, the connection zone 3 may be said to be inactive in the sense that it does not participate in the electrochemical efficiency of the device.

The electrolytic membrane 19 allows the proton diffusion of an anode to a cathode, the anode and the cathode being located opposite one another, the protons may be present within the membrane in the form of H3O + ions. It has a non-zero coefficient of permeation of hydrogen, thus allowing the diffusion of hydrogen through the membrane of the cathode to the anode. The electrolytic membrane 19 is monolithic, and is made of the same material over its entire surface area. It can thus be made from materials usually chosen by those skilled in the art, such as those marketed under the reference Nation 115 or Nation 117 in the case of an electrolyser which has a hydrogen permeation coefficient of the order of 1.25 0.14 cms / s / cm 2 at 8o ° C and at atmospheric pressure, or those sold under the reference Nafion 211 in the case of a fuel cell.

The first electrode 21 is in contact with the first face 19.1 of the electrolyte membrane 19 and receives a reactive fluid Fi, in the first distribution circuit 18.1, namely oxygen in the case of a battery to fuel or water in the case of an electrolyser. It comprises an active layer adapted to carry out an oxidation or reduction reaction of the incoming fluid Fi m, the active layer having a catalyst promoting this electrochemical reaction.

The second electrode 22 is in contact with the opposite second face 19.2 of the electrolyte membrane 19, and receives hydrogen to be oxidized in the case of a fuel cell, or generates hydrogen in the case of an electrolyser. It comprises an active layer adapted to carry out a reduction or oxidation reaction, the active layer having a catalyst promoting this electrochemical reaction.

The first and second electrodes 21, 22 are electrically connected to one another by an electric circuit 23 which allows the flow of electrons between the two electrodes 21, 22 and allows, in the case of an electrolyzer, applying an electrical potential difference between the first and second electrodes 21,22. In this case, the applied electrical voltage Vi is positive, in the sense that the electric potential imposed on the first electrode 21 is greater than that imposed on the second electrode 22. It can be between 1.3V and 3V, for example equal to at about 1.8V, for a current density of, for example, 5mA / cm2 to 4A / cm2. In the case of a fuel cell, the electric circuit 23 may comprise an electric charge at the terminals of which an electric potential difference is applied by the electrodes 21, 22.

In the case of a fuel cell, the first electrode 21 is a cathode providing a reduction reaction producing water from oxygen introduced, and protons and electrons from the second electrode 22. And the second electrode 22 is an anode providing an oxidation reaction of the introduced hydrogen. Due to the permeation of the electrolyte membrane 19, hydrogen can diffuse from the second face 19.2 to the first face 19.1 of the electrolyte membrane 19, and flow into the first cathodic distribution circuit 18.1.

In the case of an electrolyzer, the first electrode 21 is an anode ensuring an oxidation of the introduced water, and the second electrode 22 is a cathode ensuring the reduction of protons. Due to the permeation of the electrolyte membrane 19, hydrogen can also diffuse from the second face 19.2 to the first face 19.1, and flow into the first distribution circuit 18.1.

The hydrogen sensor 30 comprises an anode 31 and a detection cathode 32, both located in the connection zone 3, between the active zone 2 and the evacuation manifold 15.1, downstream of the first electrode 21. in the longitudinal direction of fluid flow from the injection manifold 14.1 to the exhaust manifold 15.1. The hydrogen sensor 30 is adapted to detect the presence of hydrogen in the first distribution circuit 18.1 by oxidation of at least a portion of the hydrogen present. The anode 31 and the cathode 32 are separated from each other by the same electrolytic membrane 19, and the sensor 30 further comprises a voltage source 33 for applying a potential difference V2 between the anode 31 and the cathode 32.

The anode 31 of detection is in contact with the first face 19.1 of the electrolyte membrane 19 and is located in the connecting zone 3 of ΓΑΜΕ n so that it is accessible by the fluid Fi, out flowing in the first distribution circuit 18.1. It is distinct from the first electrode 21 in the sense that it is electrically isolated. It comprises an active layer adapted to carry out the oxidation of hydrogen, the latter comprising a catalyst promoting this oxidation reaction, for example platinum particles supported by carbon, or even palladium. The oxidation reaction of hydrogen is written:

The cathode 32 of detection is in contact with the second face 19.2 of the electrolyte membrane 19 and is opposite the anode 31 of detection, being in communication

fluidic with the second distribution circuit 18.2. It is distinct from the second electrode 22 in the sense that it is electrically isolated. It comprises an active layer adapted to carry out the reduction of the protons having diffused through the electrolyte membrane 19 with the electrons resulting from the oxidation of hydrogen. The active layer comprises a catalyst promoting this reduction reaction, for example platinum particles supported by carbon, or even palladium. The proton reduction reaction is written:

The hydrogen sensor 30 comprises a voltage source 33 for applying an electrical potential difference V2, preferably continuous, between the anode 31 and the cathode 32 of detection, thus allowing the oxidation of at least part of the hydrogen present at the anode 31, the circulation of the electrons to the cathode 32, then the reduction of the protons at the cathode 32. For example, the applied electrical voltage V2 is likewise sign that the difference of electrical potentials between the electrodes 21,22 in the case of an electrolyser or a fuel cell. In general, it has a lower value, in absolute value, than the voltage Vi and can be equal to about 0.2V, or even about 0.4V. The voltage source 33 thus comprises a voltage generator associated with an electrical circuit formed of conductive tracks connecting the voltage generator to the anode 31 and to the cathode 32.

The hydrogen sensor 30 comprises an electric current sensor 35, connected to the voltage source 33. The current sensor 35 measures the value of the current flowing or not in the electrical circuit of the voltage source 33, according to that hydrogen, initially present or not in the first distribution circuit 18.1 is oxidized at the anode 31 · The hydrogen sensor 30 also comprises a calculation unit 36, connected to the current sensor 35, which is adapted to detect the presence of hydrogen at the first face 19.1 of the electrolyte membrane 19, that is to say in the first distribution circuit 18.1. From the measured value of the electric current, the calculation unit 36 may be able to calculate the quantity of oxidized hydrogen at the anode 31. Advantageously, the calculation unit 36 integrates a database ( abacus obtained beforehand) or an electrochemical model making it possible to estimate, from the measured value of the electric current, the quantity of hydrogen circulating in the connection zone 3 at the level of the first face 19.1 of the electrolyte membrane 19, that is, in the first distribution circuit 18.1. The database may have been obtained previously, for example by connecting, for a point of the polarization curve of the

electrochemical cell 10, the quantity of hydrogen flowing in the first distribution circuit 18.1 as a function of the value of the electric current supplied by the sensor 35.

Thus, the electrochemical device 1 comprises a hydrogen sensor 30 integrated within the electrochemical cell 20, in the sense that it can detect the possible presence of hydrogen in the first distribution circuit 18.1, it is that is, on the 19.1 side of the electrolyte membrane 19 where hydrogen may have been diffused by permeation.

The hydrogen sensor 30 thus makes it possible to detect in real time the presence of hydrogen having diffused by permeation through the electrolyte membrane 19, or even to provide the amount of oxidized hydrogen at the anode 31 of detection . It advantageously makes it possible to estimate the quantity of hydrogen flowing in the first distribution circuit 18.1, at the outlet of the active zone 2. Thus, this information can be exploited to limit the risks of ignition in the case of an electrolyser and / or to know the state of health of the electrolyte membrane 19 (degree of aging, local failure, etc ...).

This avoids the need to use a specific instrumentation of the electrochemical cell 20 which can be difficult or expensive to implement. The hydrogen sensor 30 also has the advantage of reducing the volume proportion of hydrogen in the outgoing fluid Fi, out which circulates in the first distribution circuit 18.1, thereby detecting the hydrogen present by oxidation.

The operation of the electrochemical device 1 is now described in the case of an electrolyser.

Water Fi, m is injected at the inlet of the first distribution circuit 18.1 by the injection manifold 14.1, and comes into contact with the first electrode 21, which is here an anode. In this example, water F2, in can also be injected at the inlet of the second distribution circuit 18.2 by the second injection manifold 14.2. The water is oxidized at the first electrode 21 of the active zone 2, which generates oxygen circulating in the first distribution circuit 18.1, and the protons are reduced to the second electrode 22, thereby generating circulating hydrogen in the second distribution circuit 18.2.

However, hydrogen generated at the second electrode 22 diffuses by permeation through the electrolyte membrane 19 to the first electrode 21. At the output of the active zone 2, the fluid Fi, out flowing in the first Distribution circuit 18.1 thus comprises oxygen and a non-zero volume proportion of hydrogen.

Fluid Flj0Ut then flows through the connection zone 3, located between the active zone 2 and the first exhaust manifold 15.1. It thus comes into contact with the anode 31 of detection, which then performs the oxidation of at least a portion of the hydrogen present, a non-zero voltage V2 being applied between the electrodes 31, 32. The protons then diffuse until the cathode 32 and the electrons circulate in the electrical circuit of the voltage source 33. The reduction of the protons is then carried out at the cathode 32.

The current sensor 35 thus measures a non-zero value of the electric current flowing in the voltage source 33, and the calculation unit 36 detects the presence of hydrogen when the measured value is non-zero. The unit 36 can also calculate the quantity of hydrogen that has been oxidized at the anode 31. The calculation unit 36 can further estimate the quantity of hydrogen flowing in the first distribution circuit 18.1 at the outlet of the active zone. 2 from the measured value of the electric current.

Figures 3A to 3E illustrate in top view different parts of the electrochemical device 1 according to a first variant of the embodiment.

In this embodiment, the bipolar plates 13 are formed of sheets made of an electrically conductive material, the distribution circuits 18 may be obtained by stamping or molding. They thus allow electrical circulation between the first and second electrodes 21, 22. The anode 31 and the detection cathode 32 are then electrically isolated from the bipolar plates 13 but in fluid communication with the distribution circuits 18 of the latter.

FIG. 3A is a view from above of a first bipolar plate 13.1 in fluid communication with the first face 19.1 of the electrolytic membrane 19. It comprises in this example three injection manifolds: a first collector 14.1 for the fluid incoming Fi, in intended to come into contact with the first electrode 21, a second collector for the incoming fluid F2, in intended to come into contact with the second electrode, and here a third manifold for the injection of a coolant for to circulate in a cooling circuit, in the case of a fuel cell. It further comprises three evacuation manifolds: a first collector 15.1 for receiving the outgoing fluid Fi, out circulating in the first distribution circuit 18.1, a second collector for receiving the F2, out circulating in the second distribution circuit, and a third manifold for the coolant. The active zone 2 of the MEA 11 is illustrated by dotted lines, as well as the electrolyte membrane 19. Thus, the connection zone 3 of the MEA 11 is located between the active zone 2 and the first evacuation manifold 15.1. . As described in detail next, the electrolyte membrane 19 has a protruding portion 24 that protrudes beyond the contour of the bipolar plate 13.1.

Figures 3B and 3C are top views of an AME 11, the side of the first electrode 21 for Fig-3B and the side of the second electrode 22 for Fig.3C. The anode 31 is in contact with the first face 19.1 of the electrolyte membrane 19 and positioned in the connection zone 3, and the cathode 32 is in contact with the second face 19.2 and opposite the anode 31. The anode 31 as the cathode 32 are distinct, and therefore electrically isolated, respectively, from the first electrode 21 and the second electrode 22.

The electrolyte membrane 19 has a protruding portion 24 located at a border of the connecting zone 3. The protruding portion 24 has a dimension such that it exceeds the contour of the bipolar plates 13, and is therefore accessible from outside the stack of electrochemical cells.

The current source comprises a first conductive track 34.1 which extends continuously on the first face 19.1 from the anode 31 with which it is in electrical contact to the portion 24 projecting. It comprises a second conductive track 34.2 which extends continuously on the second face 19.2 from the cathode 32 with which it is in electrical contact to the portion 24 projecting. The conductive tracks 34.1, 34.2 may take the form of a printed circuit, for example made by depositing an ink formed of a conductive material and an ionomer, advantageously having a thickness less than or equal to 10 μm. This limits the local extra thicknesses that can induce leaks or inhomogeneities of mechanical stresses. Thus, the voltage generator can be easily connected to the conductive tracks 34.1, 34.2 insofar as they extend beyond the contour of the bipolar plates.

Figures 3D and 3E are top views of a diffusion layer 12.1 (GDL for Gas Diffusion Rent, in English) having a through hole 25.1. The first diffusion layer 12.1 is intended to come into contact with the first face 19.1, and to cover the active zone 2 and the connection zone 3. To prevent the diffusion layer 12.1 from coming into contact with the anode 31 of detection, a through hole 25.1 is provided, the contour is dimensioned to avoid contact with the edge of the anode 31. Thus, it avoids the electrical contact between the diffusion layer 12.1 and the anode 31 while allowing the fluid outgoing Fi, out to join the latter. It is the same for a second diffusion layer vis-à-vis the cathode. The conductive tracks are also electrically insulated from the diffusion layers, for example by an insulating film (not shown) forming a reinforcement of ΓΑΜΕ.

Preferably, an electrically insulating but porous polymer film (not shown) may be disposed between the anode 31 and the first bipolar plate 13.1. The film may be a polymer as marketed by Celgard, for example Celgard 2500.

Thus, the electrical insulation between the anode 31 and the first bipolar plate 13.1 is reinforced, while preserving the fluidic communication between the first distribution circuit 18.1 and the anode 31. It is the same for the cathode 32 vis- with respect to the second bipolar plate 18.2.

FIG. 4 illustrates a view from above of an AME according to another variant, on the side of the first electrode 21, which is different from that of FIG. 3B essentially in that the device 1 comprises a plurality of sensors. hydrogen 30.1, 30.2, 30.3. Each hydrogen sensor 30.1, 30.2, 30.3 has an anode and a cathode disposed in the connection zone 3. The detection anodes of the different hydrogen sensors 30.1, 30.2, 30.3 are electrically isolated from each other and each placed in look at one or more channels of the first distribution circuit. The detection cathodes are located opposite the corresponding anodes. The hydrogen sensors 30.1, 30.2, 30.3 comprise first and second conductive tracks, which extend up to a portion 24 projecting from the electrolyte membrane 19. Several projecting portions may be provided, or a single protruding portion as shown here. Thus, it is possible to detect the presence of hydrogen in a localized manner, and thus to indicate if one or more distribution channels have more hydrogen than the others. This makes it possible in particular to ensure a more precise monitoring of the state of health of the electrolyte membrane 19, and to locate more precisely a possible rupture of the membrane. Microvannes can be provided, in order to close the distribution channels at which the rupture of the membrane would be located.

Figures 5A and 5B illustrate, in top view (fig.sA) and in cross section (fig.5B), different parts of the electrochemical device 1 according to a second variant of the embodiment.

In this variant, the bipolar plates 13 comprise a structured plate made of an electrically insulating material inside which conductive lines adapted to polarize the first and second electrodes 21, 22 independently of the anode 31 and cathode 32 extend. detection. Thus, the anode 31 and the detection cathode 32 are then in contact with the insulating material of the bipolar plates 13 but electrically isolated from the first and second electrodes 21, 22. The bipolar plates 13 are then of PCB printed circuit type.

FIG. 5A is a view from above of an AME 11 on the side of the first face 19.1 of the electrolyte membrane 19, and of an example of a first distribution circuit 18.1 illustrated in dotted lines.

The AME thus comprises an electrolytic membrane 19 whose first face 19.1 is coated by the first electrode 21 which delimits the active zone 2, and by the detection anode 31 located in the connection zone 3. A plurality distribution channels runs through the active zone 2 and, here for purely illustrative purposes, join in the connection zone 3 to form a homogenization zone of the flow. Other arrangements of the channels are of course possible. Thus, as examples, the distribution channels can remain separate from each other in the connection zone, or even join in groups.

Unlike the first variant, insofar as the polarization of the anode 31 and the cathode 32 of detection is provided by the bipolar plates 13, the electrolyte membrane 19 has no protruding portion receiving conductive tracks of the current source.

Figure 5B illustrates, schematically and partially, in cross section along the sectional plane A-A illustrated in Fig-5A, an example of bipolar plates 13 of PCB type according to this second variant.

Is here illustrated the AME 11, a first zone forms the active zone 2 and a second zone, distinct from the first, forms the connecting zone 3, located downstream of the active zone 2 in the fluidic continuity of the first distribution circuit 18.1, towards the first exhaust manifold 15.1 (not shown). The active zone 2 comprises the first electrode 21 and the second electrode 22 separated from each other by the electrolyte membrane 19, and the connection zone 3 comprises the anode 31 and the cathode 32 separated from each other. The anode 31 and the first electrode 21 are distinct from one another to avoid any electrical contact, as are the cathode 32 and the second electrode 32. Electrolytic membrane 19 is proton conductive but insulating with respect to electrons.

The distribution circuits 18.1, 18.2 are formed by structuring the bipolar plates. Thus, the first distribution circuit 18.1 is made in the same bipolar plate 13.1 having structures defining fluid distribution channels, which being adapted to apply an electrical potential to the first electrode 21 and another different electrical potential to the anode 31 Similarly, the second distribution circuit 18.2 is formed in the same bipolar plate 13.2 having structures defining fluid distribution channels, which is adapted to apply an electrical potential to the second electrode 22 and another electrical potential, possibly different, at the cathode 32.

In this example, each bipolar plate 13.1, 13.2 is made from a PCB type printed circuit board (in English). It thus comprises a part 4i.i, 41-2 of an electrically insulating material, for example a ceramic, on and in which electrical lines extend.

With reference to the first bipolar plate 13.1 (the second bipolar plate 13.2 is here identical), the insulating portion 41.1 has an outer face 42e.i and an inner face 421.1 opposite one another along the axis thickness of the plate 13.1. The inner face 421.1 is oriented towards the first face 19.1 of the electrolyte membrane 19, and includes structures defining the distribution circuit 18.1.

The channels of the distribution circuit 18.1 are separated in pairs and bordered by a longitudinal wall 44.1 of the insulating plate 41.1, whose end forming a bearing surface in contact with the first electrode 21 or the anode 31, is at least partially coated by a so-called polarization electrical track 45.1, 46.1.

Thus, all or part of the ends of the longitudinal walls 44.1 separating and bordering the distribution channels is coated with such a polarization electrical track 45.1, 46.1. The polarization tracks 45.1 contact the first electrode 21, and the polarization tracks 46.1 contact the anode 31. The polarization tracks 45.1 are electrically isolated from the polarization tracks 46.1.

The polarization tracks 45.1, in contact with the first electrode 21, are connected to an electrical track 49.1 said contact recovery which extends on the outer face 42e.i. The contact recovery track 49.1 is connected to the polarization tracks 45.1 by first vias 47.1. The vias 47.1 are through orifices filled with an electrically conductive material, which extend along the thickness axis of the insulating plate 13.1 in the longitudinal walls 44.1.

Similarly, the polarization tracks 46.1, in contact with the anode 31 of detection, are connected to another electrical track 50.1 contact recovery which extends on the same external face 42e.i. The contact recovery track 50.1 is connected to the polarization tracks 46.1 by vias 48.1. The first and second electrical contact recovery tracks 49.1, 50.1 are electrically separated from one another.

Thus, the same bipolar plate 13.1 forms a first fluid distribution circuit 18.1 for the first electrode 21 and the detection anode 31, and makes it possible to apply to these two electrodes 21, 31 different electrical potentials. the other.

The second bipolar plate 13.2 may be identical or similar to the first bipolar plate 13.1 previously described. It is also possible to stack several electrode membrane assemblies along the thickness axis, the adjacent electrode membrane assemblies being separated by bipolar PCB type plates similar to those illustrated in FIGS.

Claims (12)

An electrochemical device (1), comprising at least one electrochemical cell (10), comprising: an electrode membrane assembly (n) formed of an electrolyte membrane (19) proton exchange, a first electrode (21) at contact of a first face (19.1) of the membrane (19), and a second electrode (22) in contact with a second opposite face (19.2) of the membrane (19), o two bipolar plates (13.1, 13.2), between which is located the membrane electrode assembly (11), traversed by at least one first discharge collector (15.1) in fluid communication with the first face (19.1) of the membrane (19), where the assembly electrode diaphragm (11) having an active zone (2) delimited by the first and second electrodes (21,22), and a connection zone (3) located between the active zone (2) and the first discharge collector (15.1) ; characterized in that it comprises at least one hydrogen sensor (30), comprising: an anode (31) positioned in the connecting zone (3) in contact with the first face (19.1) and including a catalyst adapted to ensuring the oxidation of hydrogen, and a cathode (32) in contact with the second face (19.2) and located opposite the anode (31); a voltage source (33) adapted to apply an electrical voltage between the anode (31) and the cathode (32) by an electric circuit; a current sensor (35), connected to the voltage source (33), adapted to measure the electric current flowing in the electrical circuit; o a calculation unit (36), connected to the current sensor (35), adapted to detect the presence of hydrogen at the first face (19.1) from the measured value of the electric current. 2. Electrochemical device (1) according to claim 1, wherein the calculation unit (36) is adapted to calculate the amount of oxidized hydrogen at the anode (31) from the measured value of the electric current. Electrochemical device (1) according to claim 1 or 2, wherein the calculation unit (36) is adapted to calculate the quantity of hydrogen flowing in the connection zone (3) at the first face (19.1). ), from the measured value of the electric current. An electrochemical device (1) according to any one of claims 1 to 3, wherein a first bipolar plate (13.1) has a first fluid distribution circuit (18.1) in communication with said first flow collector (15.1) and having at least one distribution channel superimposed on the anode (31). 5. Electrochemical device (1) according to any one of claims 1 to 4, wherein each bipolar plate (13.1, 13.2) is formed of at least one sheet made of an electrically conductive material. Electrochemical device (1) according to claim 5, wherein the anode (31) and the cathode (32) are electrically isolated from the bipolar plates (13.1, 13.2). An electrochemical device (1) according to claim 5 or 6, wherein the electrolyte membrane (19) has a protruding portion (24) located in a border of the connection zone (3), the voltage source (33). having a first conducting track (34.1) secured to the first face (19.1) of the diaphragm (19) and connecting the anode (31) to the protruding portion (24), and a second conducting track (34.2) secured to the second face (19.2) and connecting the cathode (32) to the portion (24) projecting. 8. Electrochemical device (1) according to claim 7, wherein the first and second conductive tracks (34.1, 34.2) have a thickness less than or equal to iopm. 9. Electrochemical device (1) according to any one of claims 1 to 4, wherein a first and a second bipolar plates (13.1, 13.2) are each formed in a plate (41.1,41.2) made of an electrically insulating material, and having conductive lines (45, 47, 546, 46, 48, 50) arranged to bias, respectively, the first electrode (21) independently of the anode (31), and the second electrode (22) independently of the cathode (32). Electrochemical device (1) according to claim 9, wherein the first bipolar plate (13.1) is made in one piece, and has an inner face (421.1) and an outer face (42e.i), the inner face (421.1) having structures forming a fluid distribution circuit (18.1), the first bipolar plate (13.1) being adapted to apply a first electrical potential to the first electrode (21) and a second electrical potential to the anode (31) different from the first potential. An electrochemical device (1) according to claim 10, wherein the insulating material (41.1) of the first bipolar plate (13.1) defines the inner face (421.1) and the opposite outer face (42e.i), the inner face ( 421.1) having fluid distribution channels longitudinally separated in pairs by a longitudinal wall (44.1) engaging the first electrode (21) or the anode (31) by a bearing surface, electrically conductive lines ( 45.1,46.1) extending at the longitudinal wall bearing surfaces (44.1) and being adapted, for a first set (45.1) of them, to apply an electric potential to the first electrode (21) and, for a second set (46.1) of them, to apply to the anode (31) a different electrical potential. 12. Electrochemical device (1) according to claim 11, wherein the first bipolar plate (13.1) comprises a first (49.1) and a second (50.1) said conductive lines of contact recovery extending on the outer face (42e. 1), and first (47.1) and second (48.1) conductive vias extending between the outer face (42e.i) and the inner face (421.1) in the longitudinal walls (44.1), the first conductive line (49.1). contact resumption being adapted to apply an electrical potential to the first set (45.1) of conductive lines by conductive vias (47.1), and the second conductive line (50.1) contact recovery being adapted to apply a different electrical potential to the second together (46.2) conductive lines by the other conductive vias (48.1).